Agropolymer material for use in water purification and a method of producing the same

ABSTRACT

The present invention relates to novel agropolymers, which comprise a carbohydrate and/or silica matrix substantially devoid of proteins, tannins and polyphenols and which comprise metal binding reactive sites. A method of producing the agropolymers is also disclosed wherein the agropolymers are derived from plant materials such as seed coats, seed covers, husks, or hulls of various agricultural crops. The agricultural crops typically used to produce the agropolymers include  Oryza sativa, Panicum miliaceum, Setaria italica, Cajanus cajan, Vigna mungo, Vigna radiata, Triticum  sp.,  Ricinus communis, Helianthus annus, Gossypium  sp., and  Arachis  sp. The agropolymers of the present invention are capable of purifying aqueous solutions polluted or contaminated with metals and/or ions. Thus, the present invention also discloses a method whereby agropolymers are used in the purification of contaminated water and other aqueous solutions. The agropolymers disclosed herein are useful in several industrial applications including purifying polluted drinking water or ground water.

This application is a divisional of U.S. patent application Ser. No.09/938,757 filed Aug. 24, 2001, now U.S. Pat. No. 6,958,232 issued Oct.25, 2005, which is a continuation of International Application NumberPCT/IN00/00015, filed Feb. 24, 2000 and published in English asInternational Publication Number WO 00/50167 on Aug. 31, 2000, whichclaims priority to Indian Patent Application Number 222/MAS/99 filedFeb. 24, 1999 and Indian Patent Application Number 223/MAS/99 filed Feb.24, 1999, to each of which priority is claimed, and each of which isincorporated by reference in its entirety herein.

FIELD OF THE INVENTION

The present invention generally relates to the field of agriculturalbiotechnology. In particular, this invention pertains to a novelagropolymer and a method of manufacturing the agropolymer from plantparts such as seed coats, hulls, husks or seed covers of plantsincluding agricultural crops. The agropolymers disclosed herein haveextensive industrial applications and may be useful in purifying wateror aqueous solutions polluted or contaminated by metal or ions.

BACKGROUND OF THE INVENTION

Several biologically originating metal sequestration agents are known inthe art. Examples of such agents include tannins, humic acid, whole cellbiomass, chitin and chitin derivatives, metallothioneins, microbialpolysaccharides, melannins, polyphenolic biopigments, bacterial cellwall polymers, microbially produced chelating agents (siderophores), andthe like. However, the above materials may be costly and often are notavailable in sufficient quantities. Specifically, the substances knownin the art have not been successfully produced on large scale forindustrial use because of the low availability of raw materials and thehigh production costs.

Furthermore, the substances known in the art may be less effective thanthe agropolymer disclosed herein. Thus, the present invention is aimedat producing agropolymers, which are effective in sequestering metalsand ions from polluted or contaminated aqueous solutions and whichderive from inexpensive, widely available plant materials, preferablyraw agricultural materials, such as seed coats, hulls, husks, or seedcovers of agricultural crops.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide novel agropolymersthat originate from plant materials, such as the seed coats, husks,hulls, or seed covers of agricultural crops. Agricultural crops whichmay be employed in forming the agropolymers of the present inventioninclude Oryza sativa, Panicum miliaceum, Setaria italica, Cajanus cajan,Vigna mungo, Vigna radiata, Triticum sp., Ricinus communis, Helianthusannus, Gossypium sp., and Arachis sp.

Another object of the present invention is to provide an agropolymermaterial that originates biologically and that is non-toxic,biodegradable, inexpensive, widely available, and effective. Such anagropolymer may be derived from agricultural sources.

Still another objective of the present invention is to develop a methodfor producing the agropolymer materials disclosed herein and a method ofusing the agropolymers in industrial applications such as sequesteringor removing metals or ions from water or aqueous solutions. Suchindustrial applications would enable the agropolymer to aid in improvingwater pollution control and reducing overall environmental pollution.

Yet another object of the present invention is to provide a method ofremoval of heavy metals and ions from aqueous solutions using theagropolymers disclosed herein.

Still another objective of the present invention is creating a method ofwater purification which uses natural, biological agriculturalresources, which are abundant in nature and thus readily available.

Therefore, a further object of the present invention is to provide amethod of producing an agropolymer material comprising a carbohydrateand/or silica matrix substantially devoid of proteins, tannins, pigmentsand polyphenols, wherein the agropolymer material has metal bindingreactive sites.

One skilled in the art will appreciate that the various embodimentsdisclosed herein, as well as other embodiments within the scope of theinvention, will have numerous applications in the environmental,chemical, and biological fields.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be better understood with reference to theattached drawings described below:

FIGS. 1(A), (B), and (C): IR spectra of a raw rice husk sample.

FIGS. 2(A), (B), and (C): IR spectra of a rice husk sample treated withalkaline hydrogen peroxide.

FIGS. 3(A), (B), and (C): IR spectra of a raw rice-husk sample treatedwith ferric chloride.

FIGS. 4(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated rice husk sample, which was subsequently treated with ferricchloride.

FIGS. 5(A), (B), and (C): IR spectra of a raw Setaria italica husksample.

FIGS. 6(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated Setaria italica husk sample.

FIGS. 7(A), (B), and (C): IR spectra of a raw Setaria italica husksample treated with ferric chloride.

FIGS. 8(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated Setaria italica husk sample which was subsequently treated withferric chloride.

FIGS. 9(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated wheat husk sample.

FIGS. 10(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated wheat husk sample which was subsequently treated with ferricchloride.

FIGS. 11(A), (B), and (C): IR spectra of a Panicum miliaceum husksample.

FIGS. 12(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated Panicum miliaceum husk sample which was subsequently treatedwith ferric chloride.

FIGS. 13(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated cotton seed (Gossypium sp.) hull sample.

FIGS. 14(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated cotton seed (Gossypium sp.) hull sample which was subsequentlytreated with ferric chloride.

FIGS. 15(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated castor (Ricinus communis) seed coat sample.

FIGS. 16(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated castor (Ricinus communes) seed coat sample which subsequentlywas treated with ferric chloride.

FIGS. 17(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated sunflower (Helianthus annus) seed coat sample.

FIGS. 18(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated sunflower (Helianthus annus) seed coat sample which subsequentlywas treated with ferric chloride.

FIGS. 19(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated redgram (Cajanus cajan) seed coat sample.

FIGS. 20(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated redgram (Cajanus cajan) seed coat sample which subsequently wastreated with ferric chloride.

FIGS. 21(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated greengram (Vigna radiata) seed coat sample.

FIGS. 22(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated greengram (Vigna radiata) seed coat sample which subsequentlywas treated with ferric chloride.

FIGS. 23(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated blackgram (Vigna mungo) seed coat sample.

FIGS. 24(A), (B), and (C): IR spectra of an alkaline hydrogen peroxidetreated blackgram (Vigna mungo) seed coat sample which subsequently wastreated with ferric chloride.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to providing a novel agropolymerhaving metal binding sites, which are incorporated into a matrix of theagropolymer either by alkali treatment, hydrogen peroxide treatment, ora combination alkaline hydrogen peroxide treatment. More particularly,this invention relates to the use of the agropolymer disclosed herein inthe purification of water or aqueous solutions polluted by metals orions, including the purification of industrial ground water and drinkingwater. Such a purification method is possible because of the capabilityof the agropolymer to sequester metals and/or ions found in polluted orcontaminated water or aqueous solutions.

The matrix of the agropolymer is obtained from any plant parts such asseed coats, seed covers, hulls and husks. The metal binding reactivesites (which facilitate organometallic bonds) are created by reactingthe agropolymers with metals as observed under infrared (IR)spectroscopy.

The agropolymers of the present invention may be produced from plantmaterials (such as seed coats, seed covers, hulls, or husks) ofagricultural crops, and the crops appropriate for use herein may includeOryza sativa, Panicum miliaceum, Setaria italica, Cajanus cajan, Vignamungo, Vigna radiata, Triticum sp., Ricinus communes, Helianthus annus,Gossypium sp. Arachis sp. These crops are used in certain preferredembodiments because they better facilitate the sequestration of metalsand ions.

In certain embodiments of the present invention, the method of producingthe agropolymers disclosed herein begins with the plant material (suchas the seed coat, seed cover, hull, or husk) being powdered. Inpreferred embodiments, the powdering of the plant material is effectedby a grinder. The plant material is subsequently micronized, which isaccomplished by using a micronizer to obtain desired particle size (tobe measured in microns).

The micronized plant material then undergoes either alkali treatment,hydrogen peroxide treatment, or a combination alkaline hydrogen peroxidetreatment. In certain preferred embodiments, the alkali treatment iseffected with sodium hydroxide, potassium hydroxide, sodium carbonate,or the like. In typical embodiments, the alkali solutions used to treatthe micronized plant material have concentrations of alkali material inwater of from about 1% by weight to about 10% by weight.

In other embodiments, the micronized plant material samples undergohydrogen peroxide treatment either in combination with the alkalitreatment or alone (without an alkali solution). In these embodiments,hydrogen peroxide is typically employed at a concentration of from about5% by weight to about 30% by weight.

In embodiments where the combination alkaline hydrogen peroxidetreatment is employed, the alkaline treatment may be performed eitherbefore hydrogen peroxide treatment, along with hydrogen peroxidetreatment, or after hydrogen peroxide treatment. In certain preferredembodiments, the plant material undergoes the alkaline treatment and thehydrogen peroxide treatment simultaneously.

The above described treatments (including alkali treatment, hydrogenperoxide treatment, or combination alkaline hydrogen peroxide treatment)serve to create the property of enhanced metal or ion sequestration forthe resultant agropolymer molecules.

After either alkaline treatment, hydrogen peroxide treatment, or acombination alkaline hydrogen peroxide treatment, the treated plantmaterial is washed repeatedly with water or an acid solution to removeany alkaline and/or hydrogen peroxide residue. The acid solutionstypically used in this step include solutions of diluted H₂SO₄, HCl, orHNO₃.

The treated plant material is further contacted with an acid solution toremove any bound metals. If bound metals are present in the agropolymermaterial, such metal ions are eluted with acid solutions (typically ofH₂SO₄, HCl, or HNO₃) having concentrations of acid in water of fromabout 1% by weight to about 3% by weight.

The resulting agropolymer molecules are subsequently neutralized (toremove any remaining acid) through water washings or by the addition ofa diluted alkali solution. The diluted alkali solution is typically asolution of about 1.0 M sodium hydroxide or potassium hydroxide.

Lastly, the resultant agropolymer molecules are removed from thesupernatant through decantation and are dried to remove the remainingmoisture content. This drying takes place either at room temperature orwith the aid of a dryer at a temperature of from about 70° C. to about80° C.

The yield of agropolymer depends on the source of the plant material,the size of the plant material before treatment, and the reactionprocedure or treatment adopted. Generally, yields of about 30 to 40% ofthe agropolymer were obtained when producing smaller agropolymersamples. Conversely, yields of about 75 to 80% of the agropolymer wereobtained when producing larger agropolymer samples (for example,agropolymer samples larger than 150 microns). General analysis of theagropolymer yields show that the smaller agropolymer molecules arebetter able to sequester metals and/or ions.

In certain embodiments, the alkaline treatment without hydrogen peroxideis employed for producing agropolymers from cereals and millets. Themicronized seed coats or hulls are first mixed with an alkaline solution(such as sodium hydroxide or potassium hydroxide). This alkalinetreatment may be carried out either by the addition of an alkalinesolution to the micronized seed coat or hull powder or by directaddition of alkaline powder or flakes to the micronized seed coat orhull powder followed by addition of water.

In embodiments involving alkaline treatment, the treated plant materialreleases a dark brownish-yellow substance. In these embodiments, the useof lower percentages of alkali (for example amounts of from about 5% toabout 7.5%) requires more time to remove the dark brownish-yellowsubstance from the seed coats or hulls. However, the use of higherpercentages of alkali (for example solutions of from about 20% to about25% alkali) removes the dark brownish-yellow substance within about 3-4hours.

Agropolymers developed according to the present invention have extensiveindustrial applications. They can be used effectively for pollutioncontrol in order to protect water and aqueous solutions in theenvironment from metal or ion contamination. In preferred embodiments,metals such as iron, copper, aluminum, arsenic, mercury, lead, and zincas well as various ions may be removed from water and other aqueoussolutions using the agropolymer disclosed herein.

In the present method, contaminated or polluted aqueous solutions(including metal-polluted or ion-polluted drinking water and groundwater) are treated with agropolymers and/or metal-impregnatedagropolymers. First, the polluted water is contacted with theagropolymers and/or the metal-impregnated agropolymers using a column orbatch mode. This effects the ion or metal sequestration, therebyresulting in pollution-free water. The sequestration is typicallycarried out under optimum conditions wherein factors such as pH areclosely regulated for maximum sequestration efficiency. In preferredembodiments, the agropolymers disclosed herein are capable of removingmetals or ions from water or other aqueous solutions at the parts permillion (PPM) to parts per billion (PPB) level.

Possible sites for the use of the agropolymers disclosed herein includeareas where ground water is contaminated by toxic metals. For example,in certain embodiments, natural ground water, which is rich in arsenic,may be treated with the agropolymers of the present invention, and thearsenic content is significantly reduced so that the previouslyarsenic-rich water becomes potable water.

The following examples are intended to illustrate the invention andshould not be construed as limiting the invention in any way.

EXAMPLES Example 1 IR Spectroscopy Results of Various Agropolymers

In these examples, raw husks, hulls or seed coats were micronized, andIR spectroscopy was performed using KBr pellets. The agropolymer samplesused herein were treated with ferric chloride and dried before the IRspectroscopy was performed. IR spectroscopy of each sample was performedin three patterns: (A) total scans, representing 4000 to 500 wavenumbers(cm⁻¹); (B) scans from 4000 to 2200 wavenumbers (cm⁻¹); and (C) scansfrom 2000 to 600 wavenumbers (cm⁻¹). Thus, in FIGS. 1-24, each figure isdenoted (A), (B), or (C), and this denotation represents the IRspectroscopy pattern from the list above that was performed in theparticular example.

As shown in FIGS. 1-4, IR spectra of various samples of rice huskrevealed that the alkaline hydrogen peroxide treatment to rice huskresulted in more reactive bonds or more organometallic bonds.

As shown in FIGS. 5-8, the IR spectra revealed more reactiveorganometallic bonds when samples of the Setaria italica husk weretreated with iron.

FIGS. 9 and 10 reveal that alkaline hydrogen peroxide treated wheat(Triticum sp.) husk resulted in many organometallic bonds, particularlyat 2360±10 and 2340±10 wavenumbers (cm⁻¹).

The IR spectra of FIGS. 11 and 12 reveal that organometallic bonds weremore predominant for Panicum miliaceum husk samples from 1600 to 600wavenumbers (cm⁻¹).

As shown in the IR spectra in FIGS. 13 and 14, alkaline hydrogenperoxide treated cotton seed (Gossypium sp.) hulls resulted in manyorganometallic bonds, particularly at 2360±10 and 2340±10 wavenumbers(cm⁻¹).

As shown in the IR spectra of FIGS. 15 and 16, alkaline hydrogenperoxide treated castor seed coats (Ricinus communis) resulted in manyorganometallic bonds.

As shown in the IR spectra of FIGS. 17 and 18, alkaline hydrogenperoxide treated sunflower seed coats (Helianthus annus) resulted inmany organometallic bonds.

As shown in IR spectra of FIGS. 19 and 20, alkaline hydrogen peroxidetreated redgram seed coats (Cajanus cajan) resulted in manyorganometallic bonds.

As shown in the IR spectra of FIGS. 21 and 22, alkaline hydrogenperoxide treated greengram (Vigna radiata) seed coats resulted in manyorganometallic bonds, particularly at 2360±10 and 2340±10 wavenumbers(cm⁻¹).

As shown in the IR spectra of FIGS. 23 and 24, alkaline hydrogenperoxide treated blackgram (Vigna mungo) seed coats resulted in manyorganometallic bonds.

Generally, the IR spectra compiled and described above show thecapability of organometallic bonding held by agropolymers formed fromvarious agricultural crops according to the present invention.

Example 2 Examination of Metal Sequestration of Agropolymers Derivedfrom Seed Coats or Hulls of Oryza Sativa, Panicum Miliaceum, and SetariaItalica

In this example, two 1.0 gram agropolymer samples were placed in 1000 mLvolumetric flasks, which were filled to 1000 mL with 20.0 PPM standardcopper and silver solutions respectively. These agropolymer samples wereproduced using the alkaline treatment method. The solutions were thenkept for 2 hours with regular shaking in between, and were subsequentlyfiltered. The resulting copper and silver present in the solutions wasthen estimated spectrophotometrically. The difference between the metalcontent present in solution before and after addition of agropolymerindicates the metal absorbing or sequestering capability of theparticular agropolymer used.

Table 1 depicts the results of sequestered copper and silver byagropolymers.

TABLE 1 METAL SEQUESTRATION OF AGROPOLYMERS PRODUCED BY ALKALINETREATMENT METHOD SILVER CONTENT COPPER CONTENT (MILLIGRAMS) (MILLIGRAMS)SEQUESTERED BY AGROPOLYMER SEQUESTERED BY 1.0 1.0 GRAM Sample PRODUCEDFROM SEED GRAM AGROPOLYMER AGROPOLYMER No. COATS OR HULLS OF: SAMPLESAMPLE 1. Setaria italica 6.0 4.1 2. Panicum miliaceum 1.6 2.5 3. Oryzasativa 4.5 4.7

As seen above, a 1.0 gram sample of the Setaria italica agropolymerabsorbed or sequestered 6.0 and 4.1 milligrams of copper and silverrespectively. Also, a 1.0 gram sample of Panicum miliaceum agropolymersequestered 1.6 and 2.5 milligrams of copper and silver respectively. A1.0 gram sample of the Oryza sativa agropolymer sequestered 4.5 and 4.7milligrams of copper and silver respectively.

Example 3 Examination of Metal Sequestration Using Metal-ImpregnatedAgropolvmers

Agropolymers exhibit a higher capability of metal sequestration insolutions containing higher metal concentrations. Thus, further studieswere performed in order to allow the agropolymers to absorb more metalin higher metal concentration solutions with longer retention times ofup to 12 to 24 hours. Agropolymers were added to solutions containingmetals such as iron or aluminum, and unbound metal was removed bythorough washings with water and/or by neutralization with alkali incases where the reaction medium had an acidic pH. Subsequently, thematerial was dried. Metal-impregnated agropolymer was then placed in abeaker, wherein 250 mL of water was added and stirred well. Then, theagropolymer material was filled on a column mode. The agropolymermaterial present in the column was washed with 50 mL of 1.0 M acid toobtain bound metal. The metal content in acid washings was estimatedspectrophotometrically. Table 2, shown below, depicts the amount of themetal content bound on the agropolymers.

TABLE 2 BOUND METAL CONTENT PRESENT IN METAL-IMPREGNATED AGROPOLYMERSPRODUCED BY ALKALINE TREATMENT METHOD METAL CONTENT AGROPOLYMER(MILLIGRAMS) PRODUCED FROM SEED SEQUESTERED BY 1.0 Sample COATS ORHULLS + GRAM AGROPOLYMER No. METAL SAMPLE 1. Setaria italica + 14.4ALUMINUM CHLORIDE 2. Oryza sativa + 8.6 ALUMINUM SULFATE 3. Setariaitalica + 4.7 FERRIC CHLORIDE

As seen above, a 1.0 gram sample of Setaria italica agropolymerimpregnated with aluminum chloride absorbed an amount of 14.4 milligramsof aluminum. A 1.0 gram sample of Oryza sativa agropolymer impregnatedwith aluminum sulfate absorbed an amount of 8.6 milligrams of aluminum.A 1.0 gram of Setaria italica agropolymer impregnated with ferricchloride absorbed an amount of 4.7 milligrams of iron.

Example 4 Examination of Arsenic Sequestration Using Agropolymers

In this example, agropolymers bound with copper, zinc, and iron wereused separately in determining the arsenic sequestering nature of suchmetal-impregnated agropolymers. 1.0 gram samples of agropolymer wereadded to 100 mL solutions containing 6.6 PPM sodium arsenate. Thesolutions were stirred well for a period of 3 to 4 hours. The arseniccontent present in the supernatant was estimated spectrophotometrically.As shown below in Table 3, the metal-impregnated agropolymerssuccessfully absorbed significant amounts of arsenic from aqueoussolutions. The copper, iron, and zinc-impregnated Setaria italicaagropolymers absorbed from about 73 to about 75 percent of the arsenicpresent in solutions whose initial arsenic contents were 6.6 PPM.

TABLE 3 ARSENIC SEQUESTRATION OF METAL-IMPREGNATED AGROPOLYMERS PRODUCEDBY ALKALINE TREATMENT METHOD ARSENIC SEQUESTERED BY AGROPOLYMER 1.0 GRAMPRODUCED FROM SEED AGROPOLYMER Sample COATS OR HULLS + INITIAL ARSENICSAMPLE No. METAL CONTENT (PPM) (PERCENTAGE) 1. Setaria italica + COPPER6.6 73.18 SULFATE (IMPREGNATED) 2. Setaria italica + FERRIC 6.6 73.3CHLORIDE (IMPREGNATED) 3. Setaria italica + ZINC 6.6 75 CHLORIDE(IMPREGNATED)

Further studies showed that agropolymers without metal impregnation werealso successful at absorbing arsenic. As shown in Table 4, agropolymerssignificantly reduced the arsenic content of natural waters containingarsenic. The samples of natural waters containing arsenic used hereinwere collected in West Bengal State in India.

TABLE 4 ARSENIC SEQUESTRATION OF AGROPOLYMERS IN NATURAL WATERSCONTAINING ARSENIC ARSENIC CONTENT INITIAL ARSENIC PRESENT IN NATURALCONTENT WATERS AFTER AGROPOLYMER PRESENT IN TREATMENT WITH SamplePRODUCED FROM SEED NATURAL AGROPOLYMERS FOR No. COATS OR HULLS WATERS 12HOURS 1. Setaria italica 325 PPB 40 PPB 2. Oryza sativa 325 PPB 50 PPB

Example 5 Examination of Fluoride Sequestration Using Agropolymers

In this example, it was observed that agropolymers cannot absorbfluoride ion except when the agropolymer is bound with metals such asaluminum. Agropolymers bound with aluminum sulfate were added to asolution containing 5 PPM sodium fluoride. Specifically, 1000 milligramsof metal-impregnated agropolymer were added to 50 mL of a 5 PPM sodiumfluoride solution. Two metal-impregnated agropolymer samples absorbedfluoride ion in amounts of 77.4% and 90.87 % respectively.

These metal-impregnated agropolymer samples were also able to removefluoride ion from natural water samples containing fluoride. When anatural water samples having 4.15 PPM fluoride content were mixed withan aluminum chloride-impregnated Setaria Italica agropolymer sample andan aluminum sulfate-impregnated Oryza Sativa agropolymer samplerespectively, in the amount of 1.0 gram agropolymer sample per liter ofwater, significant fluoride ion removal was observed.

Example 6 Examination of the Effects of pH Levels on Metal Sequestrationof Agropolvmers

In this example, the parameters for best metal sequestration and boundmetal elution were studied. The effectiveness of the agropolymersdisclosed herein is dependent upon pH levels suitable for metalsequestration. Typically, metals bound to the agropolymers disclosedherein can be eluted with mineral acids including sulfuric acid, nitricacid, or hydrochloric acid at pH levels of from about 0.8 to about 1.0.Furthermore, the agropolymer materials typically have maximum metal orion sequestering capabilities at neutral pH ranges for most of themetals tested.

Example 7 Examination of Iron Sequestration Using Agropolymers

In this example, ferric chloride solution was passed through 1.0 gramsamples of various agropolymers in a column at a flow rate of 2 mL perminute. The agropolymers had been treated using the alkaline hydrogenperoxide treatment, and bound metal content was estimated by eluting thebound metal with solutions of about 2% to 5% hydrochloric acid. Beforeelution, the unbound excess metal from the column was removed by washingwith 2.5 pH hydrochloric acid solution. The bound metal content wasestimated spectrophotometrically using par reagent at a wavelength of535 nm.

Table 5 depicts the iron sequestration of agropolymers derived fromOryza sativa, Panicum miliaceum, Setaria italica, Cajanus cajan, Vignamungo, Vigna radiata, Triticum sp., Ricinus communis, Helianthus annus,Gossypium sp., and Arachis sp.

TABLE 5 IRON SEQUESTRATION OF AGROPOLYMERS PRODUCED BY ALKALINE HYDROGENPEROXIDE TREATMENT METHOD IRON CONTENT (MILLIGRAMS) AGROPOLYMERSEQUESTERED BY 1.0 Sample PRODUCED FROM SEED GRAM AGROPOLYMER No. COATSOR HULLS OF: SAMPLE 1. Oryza sativa 5.15 2. Panicum miliaceum 3.125 3.Setaria italica 5.0 4. Cajanus cajan 11.75 5. Vigna mungo 6.875 6. Vignaradiata 17.18 7. Triticum sp. 3.125 8. Ricinus communis 2.3 9.Helianthus annus 11.25 10. Gossypium sp. 6.25 11. Arachis sp. 20.56 (Redseed coat or cover of groundnut)

Generally, the results of the above examples illustrate the usefulnessand effectiveness of agropolymers and metal-impregnated agropolymers inaffinity columns, or the like, to purify aqueous solutions by binding,removing, sequestering, or reacting with reactive metals and ions. Thus,the agropolymer materials may be useful in various industrialapplications including, but not limited to, the reduction of groundwater contamination by industrial waste water, the improvement ofaffinity chromatography systems, and possibly even the manufacture ofvarious agropolymer derivatives (such as biodegradable plastics, resins,or carrier materials).

1. A method of producing an agropolymer comprising a carbohydrate andsilica matrix obtained from plant parts of an agricultural crop, saidagricultural crop selected from the group consisting of Oryza sativa,Panicum miliaceum, Setaria italica, Cajanus cajan, Vigna mungo, Vignaradiata, Triticum sp., Ricinus communis, Helianthus annus, Gossypium sp,and Arachis sp, said carbohydrate and silica matrix being substantiallydevoid of proteins, tannins, pigments and polyphenols, said matrixfurther comprising metal binding reactive sites, said method comprising:a. powdering said plant parts; b. micronizing said powdered plant parts;c. treating said micronized plant parts with either an alkalinetreatment, a hydrogen peroxide treatment, or a combination of analkaline treatment and a hydrogen peroxide treatment; d. furthertreating said plant parts with repeated washings of either water or anacid solution to remove alkaline and/or hydrogen peroxide residue fromsaid plant parts obtained from step (c); e. eluting metals bound to saidtreated plant parts from said plant parts obtained from step (d) with anacid solution; f. neutralizing said plant parts by removing remainingacid residue from said plant parts obtained from step (e) through waterwashings or through the addition of a diluted alkaline solution; and g.drying the resulting agropolymer derived from said plant parts.
 2. Themethod of claim 1, wherein said powdering of said plant parts isperformed by a grinder.
 3. The method of claim 1, wherein saidmicronizing of said powdered plant parts is effected using a micronizer.4. The method of claim 1, wherein said plant parts of said agriculturalcrop are selected from the group consisting of seed coats, seed covers,husks, and hulls.
 5. The method of claim 1, wherein said treating ofsaid micronized plant parts with said combination of an alkalinetreatment and a hydrogen peroxide treatment is effected by firsttreating said micronized plant parts with sodium carbonate andsubsequently treating said micronized plant parts with hydrogenperoxide.
 6. The method of claim 1, wherein said treating of saidmicronized plant parts with said alkaline treatment is effected byadding an alkaline solution to said micronized plant parts of saidagricultural crop.
 7. The method of claim 1, wherein said treating ofsaid micronized plant parts with said alkaline treatment is effected byadding alkaline powder or flakes directly to said micronized plant partsand subsequently adding water.
 8. The method of claim 1, wherein saidacid solution of step d is selected from the group consisting of asulfuric acid solution, a hydrochloric acid solution, and a nitric acidsolution.
 9. The method of claim 1, wherein said acid solution of theeluting step has a concentration of from 1% to 3% by weight of the acidin a water solution, and the acid solution is sulfuric acid,hydrochloric acid or nitric acid.
 10. The method of claim 1, whereinsaid diluted alkaline solution of step f is selected from the groupconsisting of a sodium hydroxide solution and a potassium hydroxidesolution.
 11. The method of claim 1, wherein said drying of saidresulting agropolymer is effected by decanting off supernatant anddrying molecules of said resulting agropolymer in a dryer at atemperature of from about 70 ° C. to about 80° C.
 12. The method ofclaim 1, wherein said drying of said resulting agropolymer is effectedby decanting off supernatant and drying molecules of said resultingagropolymer at room temperature.